Golf balls having electronically - detectable inserts

ABSTRACT

Golf ball with a central cavity ( 6, 23 ) having an RFID/electronic tag ( 4, 24 ) located therein. The tag is immersed in a medium ( 5 ) which, in response to striking of the ball, flows around the tag to damp transitional movement and vibration. For retro-fit of an already-manufactured standard ball, entry of aqueous liquid into the cavity ( 6 ) is from a borehole-opening ( 3 ) which is centered within a dimple of the outer cover ( 1 ) of the ball and sealed ( 8 ), following introduction of a gelling agent ( 9 ). After the central cavity ( 22 ) is filled with a liquid medium ( 23 ), it is closed by a plastics plug ( 25 ). The tag ( 42 ) of a used/damaged ball ( 39 ) can be retrieved and recycled by an automated machine ( 30 ) that cuts a circumferential slit ( 40 ) through the cover and then impacts blades of a chisel ( 38 ) split the ball in two to reveal the tag.

This application claims priority from United Kingdom application no.1319959.1 filed Nov. 12, 2013 which claims priority from United Kingdomapplication no. 1308041.1 filed May 3, 2013.

FIELD OF THE INVENTION

This invention relates to golf balls of the kind having anelectronically-detectable insert, and to their manufacture.

BACKGROUND OF THE INVENTION

Golf balls of the above kind are used, for example, in conjunction withdetectors/readers at target-locations of golf-driving ranges to identifyplayers who land their golf balls successfully at those locations. Theinserts used are typically radio-frequency identification (‘RFID’) tags,and RFID readers are installed in instrumented targets that haveassociated data links, computer systems and user-interface displays.Alternative forms of insert may be used, such as magnets, ferrite rodsand devices involving one or more resonant circuits.

Golf balls are subjected to exceptionally high shock, with peakaccelerations when struck frequently exceeding 40,000 g. Thispotentially reduces the useful service life of most golf balls of thekind having an electronically-detectable insert, and objects of thepresent invention are to provide a form of golf ball of this kind, and amethod of its manufacture in which the effect of shock is to a largeextent minimized.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided agolf ball of the kind having an electronically-detectable insert,wherein the insert is located in a cavity within the body of the ballimmersed in a medium which in response to striking of the ball flows asa liquid round the insert within the cavity.

According to another aspect of the invention a method of manufacturing agolf ball of the kind having an electronically-detectable insert,includes the steps of forming a cavity within a core of the golf ball,entering the insert in the cavity immersed in a medium which in responseto striking of the ball flows as a liquid round the insert within thecavity.

In both aspects of the invention, the medium in which the insert isimmersed may be an aqueous liquid or a thixotropic gel or a medium thatis part liquid and part thixotropic gel. The liquid flow round theinsert in response to the ball being struck tends by virtue ofhydrodynamic drag to damp translational movement and vibration of theinsert to an enhanced degree compared with that obtained with aresilient or cushioning medium in the cavity.

The cavity in which the insert is located may be centrally of the ball,and in all its dimensions may be at least twenty per cent, orpreferably, thirty-three per cent, larger than the correspondingdimensions of the insert. Also, entry into the cavity may extendradially into the ball from a sealed opening through the outer surfaceof the ball, and where the outer surface of the ball is dimpled, thesealed opening may be centred on a dimple of the outer surface.Furthermore, the cavity may be located in the blind bottom of a radialborehole that is bored through the centre of the golf ball and is sealedclosed with the insert located centrally of the ball.

The immersed insert may be a magnet, a ferrite rod, a device thatinvolves one or more resonant circuits, or an RFID tag.

A further object of the present invention is to facilitate recycling ofgolf balls of the kind having an electronically-detectable insert, or atleast of the insert. It is often the case with golf balls of the presentinvention that the ball itself or its outer cover needs to be replacedbefore the insert has reached the end of its useful life. Moreparticularly, where a ball with a damaged cover is involved it can becost-effective and environmentally desirable to remove the cover, andafter retaining the one-piece or multi-piece core with the insert withinit, fit a new cover over the retained core. Methods of removing coversfrom golf balls are well known and typically involve applying heat tosoften the cover (which is usually of thermoplastic that has a muchlower melting point than the rubber-compound of the core), and thenusing sharp edges to bite into the cover and scrape or pull it away fromthe core. These methods may abrade or cut the surface of the core orbreak off strongly adhering parts of it so that it is unsuitable forre-use. In these circumstances recovery and separation of the RFID tagor other insert from the core for re-use, becomes desirable forrecycling and/or economic purposes, and according to a further aspect ofthe invention, the recovery of the insert from a golf ball of the kindhaving an outer cover and an electronically-detectable insert within acore of the ball, comprises the steps of cutting a circumferential slitin the ball, the slit having a depth that extends through the outercover and partly into the surface of the core, locating chisel blades inthe slit parallel to one another on opposites sides of the centre of theball, impacting the chisel blades to split the core in half, andremoving the insert from the split core for re-use.

BRIEF DESCRIPTION OF THE DRAWINGS

Golf balls of a kind having an electronically-detectable insert, andmethods of their manufacture and recovery of theirelectronically-detectable inserts for recycling, all according to thepresent invention, will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic sectional view of a first form of golf ball havingan RFID-tag insert, according to the invention;

FIG. 2 is a schematic sectional view of the golf ball of FIG. 1 duringan intermediate stage in its manufacture;

FIG. 3 is a schematic sectional view of a second form of golf ballhaving an RFID-tag insert, according to the invention;

FIG. 4 is a schematic sectional view of the core of the second form ofgolf ball during an intermediate stage in the golf-ball manufacture, thesection in this case being taken in a plane at right angles to thesection of FIG. 3;

FIG. 5 is a schematic part-sectional side-view of a machine forautomated slitting and splitting according to the invention of golfballs of the kind having an electronically-detectable insert;

FIG. 6 is a sectional view taken on the line A-A of the ball-slittingmachine of FIG. 5 at a stage prior to splitting of acircumferentially-slit golf-ball in the recovery for recycling of itselectronically-detectable insert; and

FIG. 7 is an end view of the ball-slitting machine of FIG. 5 during astage in the recovery of the electronically-detectable insert of acircumferentially-slit golf-ball.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, the golf ball in this example is a two-piece golfball conforming to standard diameter and weight, with an outerdimpled-cover 1 and a solid core 2 (which may be single- ormulti-layered). It includes within a radial borehole 3, an RFID-taginsert 4 located centrally of the ball. The borehole 3 extends throughthe cover 1 preferably centred on a surface dimple of the cover 1, andpasses through the centre of the core 2 with its depth limited to leavea clearance dimension CD of not less than 10-13 millimetres between theblind end of the borehole 3 and the outer cover 1. The RFID-tag 4 isimmersed in a liquid 5 that fills a cavity 6 defined at the bottom ofthe borehole 3 beneath a solid gel surface-layer 7 of the liquid 5 inthe cavity 6. The borehole 3 above the layer 7 is plugged by a sealant8; as described below, the layer 7 acts as a barrier while the sealant 8is setting during manufacture of the ball.

The liquid 5 filling the cavity 6 is, for example, a mixture of fiftyper cent de-ionized water and fifty per cent ethylene glycol. Thismixture ensures that the freezing point of the liquid 5 is below −25degrees Celsius, and thereby ensures that when the ball is struck duringnormal use, there is liquid-flow round the insert 4 within the cavity 6.The hydrodynamic drag on the insert 4 created by this flow dampstranslational movement and vibration of the insert 4.

While the ball is being struck, there is a possibility of the cavity 6being deformed into a shape that might result in damage to the insert 4.As a precaution against damaged of this nature, the configuration of thecavity 6 is chosen to be in all its dimensions at least twenty tothirty-three per cent larger than the corresponding dimensions of theinsert 4. In one implementation of the ball of FIG. 1, the borehole 3has a diameter of 3.6 millimetres and the length of the cavity 6 is 16millimetres, whereas the insert 4 as enclosed within its cylindricalglass-envelope and weighing 100 milligrams, has a diameter of 2.12millimetres and a length of 12 millimetres.

Manufacture of the ball involves boring the radial borehole 3 centred ona suitable dimple of the outer cover 1, and then partially filling theborehole 3 with the aqueous solution of ethylene glycol. The insert 4 isthen entered in the borehole 3 to be fully immersed in the liquid 5throughout a depth appropriate to definition of the cavity 6 at theblind end of the borehole 3. This is followed, as illustrated in FIG. 2,by a step in which a small quantity of gelling agent 9, which may be ina powder (as illustrated) or liquid form, is poured onto the surface ofthe liquid 5 via a small funnel 10 entered in the borehole 3. Where apowder is used it may be an animal-gelatine with powder-grain between0.5 to 1.0 millimetres so that it falls cleanly through the funnel 10.

Introduction of the gelling agent into the cavity 6 causes the surfaceof the liquid 5, and possibly the liquid medium deeper, to solidify intoa thixotropic gel. When powder is used, the grains of gelatine are heldby surface tension at the surface-level of the liquid and quickly swelland congeal. There is a corresponding outcome when a liquid gellingagent is used, the result in both cases being the formation at least atthe surface of the liquid 5 in the cavity 6 of the layer 7 of solidthixotropic gel. This layer is maintained during the filling of theremainder of the borehole 3 with the sealant 8 and until the sealant hasset, so as to establish a barrier to sealant entering the liquid 5.

Once the sealant 8 has set, the ball can be taken into use and in this adrive shot played by a typical male golfer will accelerate the ballduring impact to speeds of around 60 metres per second. The contactduration during this impact is of the order of 0.4 milliseconds so theglass-encased tag 4 of the ball experiences an average force of about 15Newtons during impact. This force propels the tag 4 through theliquid/gel content of the cavity 6, and the combination of rapidmovement of the tag 5 and the walls of the cavity 6 provides intensemechanical agitation that liquefies the thixotropic gel. The consequentliquid-flow within the cavity 6 and round the tag 4 is dissipative andprovides high viscous-damping. Internal components (such as the ferriterod aerial and its resilient encapsulant) of the tag 4 are also dampedby coupling through its glass envelope. By comparison with thissituation, an RFID tag of finite mass embedded in a resilient compoundwill oscillate at near the resonant frequency of the mass-spring systemformed by the tag and the elastic coupling to the core, and thisoscillation will contribute significantly to stress levels within thetag and reduce its service life. The present invention enablessignificant improvement over this.

Small air bubbles may get trapped inside the cavity 6, and will increasethe initial compressibility of the medium within the cavity 6. This isnot a disadvantage provided that there is ample clearance between thewalls of the cavity 6 and the insert 4. The entrained air will rapidlycompress under impact and the effective compressibility will then revertto the intrinsic value of the air-free cavity 6. Slight compressibilityallows for differential thermal expansion between the material of thecore 2 and the liquid medium within the cavity 6.

The method of manufacture of the ball of FIG. 1 described above isapplicable to the retro-fitting of an already-manufactured golf ballwith an electronically-detectable insert. FIGS. 3 and 4 on the otherhand illustrate an implementation of the invention where an RFID tag isinserted during manufacture of a golf ball.

Referring to FIGS. 3 and 4, the golf ball in this case has a core 20within an overall outer cover 21 where a cavity 22 is formed in the core20 during manufacture of the core 20 itself. The cavity 22 is filledinitially with a liquid 23 and an RFID tag 24 is fully immersed in it atthe centre of the core 20.

In this version of ball, the RFID tag 24 used is an ultra high frequency(UHF) 6 mm square EMBItag type 130006006 available from Wurth ElektronicGmbH. This form of tag is very robust as it is manufactured fromfibreglass printed-circuit layers with a silicon chip embedded withinthe layers. It is thus monolithic and effectively one solid piece, 0.7millimetres thick and weighs only 50 milligrams, In order to accommodatethe larger shape of tag without removing more material of the core 20than is necessary, the opening to the cavity 22 in the core 20 ispreferably of rectangular or elongate cross-section and tapered to becompatible with a moulding process.

As shown in FIG. 4, a moulded elastomer-plug 25 is inserted into thecavity 22 and displaces the liquid 23, which spills out as shown at 26in FIG. 4. The outer portion of the plug 25 is a tight fit into themouth of the cavity 22 and may be provided with surface serrations toensure that it locks in place but also allows excess liquid to flow out.If preferred, the upper portion of the plug 25 can have a circularrather than a rectangular cross-section to aid the sealing and lockingaction.

FIG. 3 shows the plug 25 fully inserted into the core 20 leaving thebottom part of the cavity 22 housing the RFID tag 24 immersed in theliquid 23.

RFID tags are constantly being developed so new types of small RFID thatcan be read from the centre of a golf ball will become available. Forexample, a different shaped version of the EMBItag could be produced toallow a narrower cavity opening or insertion into a borehole of 4.0millimetres diameter through the cover of a golf ball as a retro-fit.Preferably the borehole diameter is not more than 4.0 millimetres so asto be contained within the diameter of a large dimple on a typicalstandard golf ball. The EMBItag can be used in near-field mode withoutan external antenna but its sensitivity is dependent on the area of itsinbuilt loop antenna, so very small area dimensions are not practical.However, in the instrumented golf target application, a short read rangeof 30 millimetres or so is acceptable. Currently, a high frequency‘NeoTAG®’ device, type F262, is available from NEOSID Pemetzrieder GmbH.This device operates at 13.56 MHz with diameter and height dimensions of2.6 millimetres maximum and is thus ideally suited to the presentapplication.

In the illustrative examples of FIGS. 1 to 4 the RFID tags are immersedin a thermo-reversible gel which is solid at room temperature but haslow melting point (for example about 30 degrees Celsius). Curing gelswhich are liquid when injected into the core-cavities and which solidifyon curing, could be used, and liquids could be used in place of gels. Inall cases the essential requirement is that the RFID tag is cocoonedwithin a filled cavity where the filler-medium is a liquid or becomesliquid during high-shock impact of the golf ball. It is important thatthe cavity does not collapse during impact and in this respect theelastic bulk modulus of the liquid or gel should be comparable to thatof the golf-ball core material and preferably not less than 1.0gigapascal.

As indicated above, it may become desirable in certain circumstances forrecycling and/or economic purposes, to recover the RFID tag or otherinsert from a damaged golf ball. Recovery of the insert is carried outaccording to the present invention by a method that involves cutting acircumferential slit in the ball to a depth that extends through theouter cover of the ball and partly into the surface of the core. Chiselblades are then located in the slit parallel to one another on oppositessides of the centre of the ball, and are impacted to split the core ofthe ball into two and allow the insert to be removed for re-use. Amachine for automating the slitting and splitting steps of the method,is illustrated in FIGS. 5 to 7 and will now be described.

Referring to FIGS. 5 and 6, the main components of the ball slitting andsplitting machine 30 comprise a feed hopper 31, a rotating ballescapement 32, downwardly-slanted rails 33, a rotating circular sawblade 34, a rotating belt 35, belt-loading rollers 36, guide fin 37 andan impact chisel 38. The blade of the chisel is divided into two by acentral cut-away as shown.

FIG. 5 shows a small quantity of balls held in the feed hopper 31 but inpractice the capacity of the hopper 31 could be greatly increased. Ballsare distributed individually from the hopper 31 by the escapement 32 todrop onto the downwardly-slanted rails 33 and pass separately into themachine without collision or interrupting continuous operation of themachine.

A golf ball 39 with contained RFID tag 42 is shown in FIG. 5 in threesuccessive positions 39(a), 39(b) and 39(c) as it passes through themachine. After dropping onto the downwardly-slanted rails 33, the ballrolls with represented clockwise rotation into the belt 35. The belt 35rotates in the opposite, anti-clockwise sense to assist ball rotationalong the rails 33 into position 39(a) and then into an upper portion ofthe saw blade 34. The blade 34 rotates in the represented anti-clockwisesense at high speed and cuts a circumferential slit through the cover ofthe ball and partly into its core. The belt-loading rollers 36 press theball firmly onto the rails 33 as it passes through the saw blade 34 andprevents any tendency for self-feed or slipping. As the ball rollsthrough the blade 34, the depth of cut varies from a minimum at thebeginning and end of the cut and a maximum at the middle. This resultsin a ‘tear shaped’ slit 40 as shown in 39(b).

Once the ball has rolled off the blade 34, its slit 40 (see FIG. 6) isengaged by the guide fin 37. The fin 37 keeps the ball correctly alignedas it rolls towards the end of the rails 33 where it then engages withstop pegs 41 under the impact chisel 38. The top part of the guide fin37 is designed to fit freely inside the slit 40 as the ball rolls fromposition 39(b) to position 39(c) but increases in thickness to hold theball steady once it reaches position 39(c).

It is important that the minimum depth of slit cut into the ball issufficient to cut through the outer cover of the ball since the cover isgenerally very tough, malleable and difficult to break other than bycutting with the saw blade. However, the maximum slit depth should notexceed CD (FIG. 1) as this could damage the cocooned RFID tag 42. Inorder to minimize the variation in slit depth, the roll radius RR (FIG.6) is chosen to be smaller than the ball diameter so that the ballrotates through a complete turn in a shorter distance compared with thecircumference of the ball. This is achieved by arranging that thecontact surfaces of the rails 33 are inclined downwardly so that theroll radius RR is then proportional to the sine of the tilt angle TA asshown in FIG. 6. In one example of the machine of FIG. 5, the saw blade34 used is a thin kerf crosscut blade of 300 millimetres diameter, thetilt angle TA is 35 degrees, and the maximum depth of slit is set to 11millimetres; this results in a minimum depth at the slit cusp of about 6millimetres.

Once the ball is located at position 39(c), the impact chisel 38 isoperated to split the ball in two as illustrated by FIG. 7. The embeddedtag 42 is exposed by this and can be removed from the body of the ballby washing out with warm water.

During a recycling and salvaging process carried out on a ball asmanufactured as described with reference to FIG. 1, the slit cut intothe ball may have a depth of 12 millimetres in any orientation of theball without cutting into the cavity 6. The thixotropic gel formed asdescribed by way of example above, has a melting point below 30 degreesCelsius and an absolute viscosity below 100 centipoise when agitated.This allows the insert 4 to be easily extracted from the split golf ballby washing out with water as referred to above, or by applying heat orboth. The use of a high viscosity medium for the filler of the cavitywould be likely to be counter-productive as this would tend to retainthe insert within the cavity. Without limitation, it is preferable forthe medium filling the cavity 9 to have an absolute viscosity less than1000 centipoise, at 20 degrees Celsius.

1. A golf ball of a kind having an electronically-detectable insert,wherein the insert is located in a cavity within the body of the ballimmersed in a medium which in response to striking of the ball flows asa liquid round the insert within the cavity.
 2. A golf ball according toclaim 1, wherein the medium in which the insert is immersed is anaqueous liquid.
 3. A golf ball according to claim 1, wherein the mediumin which the insert is immersed comprises a thixotropic gel.
 4. A golfball according to claim 1, wherein the cavity is located centrally ofthe ball.
 5. A golf ball according to claim 1, wherein the cavity in allits dimensions is at least twenty per cent larger than correspondingdimensions of the insert.
 6. A golf ball according to claim 1, whereinthe cavity in all its dimensions is at least thirty-three per centlarger than corresponding dimensions of the insert.
 7. A golf ballaccording to claim 1, wherein entry into the cavity extends radiallyinto the ball from a sealed opening through an outer surface of theball.
 8. A golf ball according to claim 7 wherein the outer surface ofthe ball is dimpled and the sealed opening is centred within a dimple ofthe outer surface.
 9. A golf ball according to claim 1, wherein theelectronically-detectable insert is one of a magnet, a ferrite rod and adevice involving at least one resonant circuit.
 10. A golf ballaccording to claim 1, wherein the electronically-detectable insert is anRFID tag.
 11. A method of manufacturing a golf ball of a kind having anelectronically-detectable insert, comprising the steps of forming acavity within a core of the golf ball, and entering the insert in thecavity immersed in a medium which in response to striking of the ballflows as a liquid round the insert within the cavity.
 12. A methodaccording to claim 11, wherein the cavity is filled with a liquid mediumvia a feed passageway that opens into the cavity, theelectronically-detectable insert is entered in the cavity through thefeed passageway to be immersed in the liquid medium within the cavity,and plugging the feed passageway.
 13. A method according to claim 12,wherein following entry of the electronically-detectable insert into thecavity, a gelling agent is added to the liquid medium within the cavityto create a gel within at least part of the cavity.
 14. A methodaccording to claim 11, wherein the medium in which the insert isimmersed is an aqueous liquid.
 15. A method according to claim 11,wherein the medium in which the insert is immersed comprises athixotropic gel.
 16. A method according to claim 11, wherein the cavityis located centrally of the ball.
 17. A method according to claim 11,wherein the electronically-detectable insert is one of a magnet, aferrite rod and a device that involves at least one resonant circuits.18. A method according to claim 11, wherein theelectronically-detectable insert is an RFID tag.
 19. A method for therecovery of an insert from a golf ball of a kind having an outer coverand an electronically-detectable insert within a core of the ball,comprising the steps of cutting a circumferential slit in the ball, theslit having a depth that extends through the outer cover of the ball andpartly into the core, locating chisel blades in the slit parallel to oneanother on opposites sides of a centre of the ball, impacting the chiselblades to split the core in two, and removing the insert from the splitcore for re-use.
 20. A method according to claim 19, wherein theelectronically-detectable insert is an RFD tag.